The present invention relates to a deformation element arrangement for a motor vehicle as well as to a motor vehicle having such a deformation element arrangement.
From German Patent document DE 102006026447 A1, an impact absorber with a variable viscosity for a motor vehicle body is known. The impact absorber has a foam structure whose rigidity can be adjusted in a controlled, variable manner by a so-called crash sensor system. The foam consists of a polymer whose pores are filled with a fluid medium. When the crash sensor system detects that a pedestrian protection is required, the impact absorber will be set to a soft state or will be left in the latter. In contrast, when the crash sensor system detects a hard impact of the vehicle, the impact absorber will be set to a hard state or will be left in the latter. The polymeric foam is filled, for example, with an electrorheological or a magnetorheological fluid. The viscosity and/or compressibility of the fluid in the polymeric foam can be changed over by means of an electric or magnetic field.
Under certain circumstances, generating an electric and/or magnetic field may be complicated, require high expenditures and be energy-intensive. Furthermore, a so-called magnetorheological fluid consists of a carrier fluid with metallic particles contained therein. In this case, the particles may be subject to wear and sedimentation, so that the function of the magnetorheological fluid may become impaired over time. In addition, known electrorheological fluids are effective only in a narrow temperature range and are sensitive to environmental influences.
It is an object of the present invention to provide a deformation element arrangement for a motor vehicle, as well as a vehicle having such a deformation element arrangement, whose deformation behavior and/or flow behavior can be changed by simple effective means over a long period of time, for example, with a low energy input.
This and other objects are achieved by a deformation element arrangement for a motor vehicle according to the present invention. The deformation element arrangement for the motor vehicle has a deformation element and a vibration-generating device. The vibration-generating device is arranged and constructed such that, when required, the deformation element can be set in vibration in such a manner that a deformation behavior and/or a flow behavior of the deformation element can be varied in accordance with the a requirement condition.
Accordingly, neither an electric field nor a magnetic field is required for setting a hardness of the deformation element, and magnetorheological as well as electrorheological fluids are not necessary. Furthermore, as required, the deformation element can simply be changed in its hardness, i.e. its deformation behavior and/or flow behavior, so that it can be set corresponding to the requirement condition.
According to a preferred further development, the deformation element has a thixotropic or rheopectic material. Advantageously, the deformation element consists essentially of a thixotropic material or essentially of a rheopectic material. A flowability of a thixotropic material is increased by a mechanical shearing stress; whereas a flowability of a rheopectic material is decreased by a mechanical shearing stress. When the respective material is set into vibration by the vibration-generating device, a mechanical shearing stress of the material will occur, with the corresponding change of the flowability and thereby a change of the deformability or hardness of the material. As a result of different operating conditions of the vibration-generating device, the deformation element can be set in its hardness or deformability.
The deformation element can preferably be mounted on the motor vehicle and constructed such that, in the event of a collision of the motor vehicle with a pedestrian, it dampens an impact of the pedestrian onto the motor vehicle. In this case, the requirement condition is an impact on the pedestrian, and a deformation behavior and/or flow behavior of the deformation element is set by way of vibrations generated by the vibration-generating device such that it is sufficiently soft.
When there is no requirement condition of an impact of the pedestrian, in a different case, the deformation element is not caused to vibrate, which means that the vibration-generating device can be inactive. As a result, the deformation element has a harder construction, so that a deformation of the deformation element, as a result of the impact/collision, takes place at a higher force level. This is advantageous in that, at a higher force level, more collision energy can be absorbed over a specific deformation distance.
According to a further development of the deformation element arrangement according to the present invention, the deformation element is adapted for the arrangement on a forward vehicle end and/or on a rearward vehicle end.
This is advantageous for the case of a frontal collision or a rear collision of the motor vehicle because, in this case, as a function of the type of collision, for example, with a pedestrian or with another motor vehicle or a rigid object, the deformation element can be set in its deformation behavior and/or flow behavior according to the requirement.
In the case in which the deformation element is arranged on a forward vehicle end and/or a rearward vehicle end, the deformation element is adapted for the arrangement on a forward vehicle end and/or on a rearward vehicle end.
This is particularly advantageous for adapting the deformation element to a pedestrian protection. An arrangement between the bumper cross member and the bumper covering permits an invisible arrangement of the deformation element. Nevertheless, in the event of a collision with a pedestrian, it has a considerable effect because, at the start of the collision, the bumper covering is the first to come in contact with the pedestrian and the deformation element is situated directly behind the bumper covering, which usually has a flexible construction.
The deformation element preferably extends essentially over an entire width of the bumper cross member. As a result, the deformation element can develop its effect irrespective of the point at which the pedestrian or the object frontally collides with the motor vehicle.
According to a preferred further development, the deformation element arrangement according to the present invention also has a control unit. The control unit is adapted such that it controls the vibration-generating device as a function of a vehicle speed. As an alternative or in addition, the control unit can control the vibration-generating device as a function of a detection of an imminent collision of the motor vehicle with an object and/or a pedestrian.
Here, the terms “control” or “controlling” also comprises “regulate” or “regulating”.
This further development is advantageous in that it is useful to change the deformation element to soft only in a defined speed range of the vehicle which is relevant to protecting pedestrians. Furthermore, it is advantageous for the deformation element to be changed with respect to its deformability or flowability only when a collision is actually imminent.
The control unit preferably activates the vibration-generating device in a speed range of the motor vehicle that is relevant to protecting a pedestrian and that is, for example, a range of between approximately 20 km/h and approximately 50 km/h. As a result, a deformability and/or a flowability of the deformation element is/are increased in this speed range.
As an alternative or in addition, the control unit can activate the vibration-generating device when an imminent collision of the motor vehicle with a pedestrian is detected.
According to a further development of the deformation element arrangement of the present invention, the vibration-generating device is adapted for generating vibrations in an ultrasonic range. For this purpose, a piezo actuator can, for example, be used.
Vibrations in an ultrasonic range can be generated particularly easily, require only low energy expenditures and have no disadvantageous influence on the motor vehicle.
In addition or as an alternative, the vibration-generating device can also be adapted such that it utilizes natural vibrations of the motor vehicle in order to set the deformation element in vibration. Natural vibrations of the motor vehicle may originate, for example, from specific drive assemblies. This further reduces the energy input for changing the deformability and/or flowability of the deformation element.
According to a preferred further development, the deformation element consists of an elastic shell filled with a thixotropic material, which shell is impermeable particularly for the thixotropic material. As an alternative, the deformation element may consist of an elastic shell filled with a rheopectic material, which shell is impermeable particularly for the rheopectic material.
As a result, it is ensured that, on the one hand, in a low-viscosity state, particularly in a fluid state or in a fluid-like state, the thixotropic material or the rheopectic material, will not flow out, In addition, the deformation element can be sufficiently deformed by the elastic shell.
In this case, it may be advantageous for the deformation element to have an opening through which the thixotropic material or the rheopectic material can be displaced onto the deformation element by the effect of a force.
In particular, it can then be displaced when it is in the low-viscosity or fluid or fluid-like state. The opening can be constructed corresponding to a valve.
In a first operating condition of the vibration-generating device, the thixotropic material or the rheopectic material is preferably highly viscous, especially solid, or has at least predominantly characteristics of a solid material. Furthermore, in a second operating state of the vibration-generating device, the thixotropic material or the rheopective material preferably is of low viscosity, particularly fluid, or has at least predominantly characteristics of a fluid.
The terms “predominantly solid” or “predominantly fluid” also comprise various gel-type states.
A thixotropic material has a time dependence of the flow properties, in the case of which a viscosity decreases as a result of continuous mechanical stress and increases again only after the stress has ended. In the present case, vibrations constitute mechanical stress; i.e. the more intensive the vibrations and therefore the mechanical stress, the more viscous or fluid and therefore softer the thixotropic material will be. The thixotropic material may be a non-Newtonian fluid.
As an alternative to a thixotropic material, according to the present invention, a rheopective material may be used for the deformation element, which has a behavior that is opposite to that of a thixotropic material. In this case, the vibration device is adapted in order to generate vibrations for making the rheopectic material less viscous or more solid and therefore harder. The rheopectic material may be a non-Newtonian fluid.
The above-indicated further developments of the invention are therefore useful and can be arbitrarily combined with one another.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.